Coloring agents for men's hair are and have been traditionally produced in the form of white emulsions which are rubbed on the hair daily and which, over a period of days and often weeks, produce a darker color on the hair. Generally they are used to darken grey hair, and produce brown or black shades thereon. For customer acceptance, such hair coloring preparations should be in the form of essentially clear liquids or white creams or lotions which do not stain the skin, particularly the hands, and should not contribute any coloring effect to the hair at the time when they are applied thereto. Such hair coloring preparations are applied to the hair in the same way that ordinary hair dressings are applied which do not have hair coloring properties, that is by hand application with combing and brushing to arrange the hair. The concept behind such hair coloring preparations is that they are rubbed on in the same manner as hair dressings and they make no noticeable effect on the hair until several days after application. After a series of applications they bring about the desired slow color change of the hair over a period of days or weeks.
To date the hair coloring preparations of this type have all contained lead salts, genreally lead acetate. These lead salts, when applied to the hair in a colorless formulation, gradually decompose and oxidize in the air to lead dioxide and/or to lead sulfide, both of which are dark pigments which color the hair to one of the darker shades. Lead salts are, however, toxic and hair dressings and coloring formulations which contain lead salts have created serious questions as to their safety. Furthermore such preparations result in unnatural looking hair, tend to rub off on clothing and bedlinens, and have a metallic sheen. Consequently it has long been the desire of the hair coloring industry to obtain colorless hair formulations which do not contain lead compounds, which can be hand-applied to the hair to convert it to a darker hue gradually over a period of time.
In conventional hair color preparations oxidation dyes are usually adjusted to a pH of 9.0 to 10.0 with ammonia. Those preparations on the market with a pH as low as 7.5 to 8.0 require pre-bleaching of the hair to obtain the desired shades. These prior products, while they give natural looking and permanent hair coloring resultsm, are dark in color, require considerable technique in application, have a strong ammoniacal odor, stain the skin, and are generally not favored for home use by men.